Abstract

Pore and fracture pressure prediction is at the heart of the well preparation workflow. Whether we are dealing with Deepwater Wells, Frontier Exploration Wells or Deviated Wells in depleted reservoirs, it is necessary to design and deliver safe and cost-effective wells. It is important to precisely anticipate overpressures, evaluating the slope of the pressure ramp-up and predicting whether reservoir pressures are in equilibrium, below or higher than the pressure of the overlying rock depending on the geological model. Uncertainties exist at different stages of the pore and fracture pressure estimation workflow and are related to several factors including: calibration wells (proximity, similar geologic context), sources of overpressure (are there any sources other than disequilibrium compaction?), uncertainties in seismic velocities, prognosed lithology, LOT data, reservoir connectivity/geological model, nature of faults, sources of overpressures, normal compaction profile, overburden gradient, etc. It is key to effectively communicate the resultant uncertainties in the PPFG results so that all different parties involved take it into consideration: The geomechanics team for wellbore stability, well design engineers and drilling teams for the well design and execution and the exploration geologists for the prospect evaluation.